Protective device.



E. M. HEWLETT. PROTECTIVE DEVICE.

APPLICATION FILED AUG.7.19I3- Patented Jam-14, 1919;

1 m r w o e t v a mm 1% he 5 M 4 EH .3 b 5 6 a m 7985 o 2| I 4 m a E. /l J 7 6 S 4 sz Wgcne M UN E TATES PATENT OFFICE,

"Eon/"nan a. HEWLETT, or scnEivEc'rAnY, aswiyeax,li ament-G ma v v ELECTRIC ooMPn vY, A oonronerron or new Yonx. 4:

v To all "whom it may concern Be it known that I, EDWARD M. HEWLETT,

a citizen'of the United States, residing at Schenectady, county or" Schenectady, Stateof New York, have invented certain new and useful Improvements in Protective Devices,

' r whichthe following-is a specification;

My invention relates to devices, such as ,relays and similar devices, which operate in which re'spond'to aln' ormal conditions on an electr c circuit witha certain amount of delay or time lag. v r i Many-devices used in electrical distribution clepend-fortheir operation upon cur -lBI1tSfWl1'10 l1 vary with and are dependent upon conditions in an'electric circuit. The proper operatlon of such devices 'I'EQUIIBS ghat'the current supplied to them shall be I *Iby-pass or safety valve for automatically ependentupon conditions. in.the electric circuit, yet at thesame time the operation of the devices may become unsatisfactory if the current'supplied to them exceeds certain v definite limits. F r example,vmany of the protective devices now used for opening'a circuit in case of overloads and similar ab normal conditions, and particularly the usual types of time limit devices, are unduly afle'cted and even temporarily deranged by very severe overloads and short circuits,-

which cause them to act practically regardless of the time limit for whlch they-are set.

This efiect is particularly disadvantageous Where a numberof protective devices respend to-the same abnormal condltlon and shouldnormally trip out in a definite and unvaryingsequence. In such a case a very heavyoverload, such asa, short circuit, may

so affect the protective. devices that they will all operate at practically the same time, or they may even operate in the wrong sequence.

The object more reliable and certain the operation'of devices which respond to currentsdependent upon conditions in an electric clrcuit, and which become erratic and unsatisfactory 1n operation when subjected to currents in excess of certain limits. A further object of my. invention is to render protective de} vices,v especially time llmit protective devices, more reliable and certain in action,

Application filed August- 7?,

'vide means for-so modifying-"or control of my invention is to render atent d Ja n 1913. Serial 1%. 733,460.

especially when very "severefoverloadsfoo short circuits and similar extremeconditions' arepresent upon the circuit, and inggeneral to improve the construction and operation of devices of this character. To this e'zid I: I

the effect of an -overload or otherextreme condition upon the device-responsive-ltothe current dependent upon that conditiontliat' thedevice retains its characteristics and c mode of operation in spite of the extreme conditions upon the circuit. For-example, the effect of. an overload upon the'overloa'd relay is automatically modified or controlled to preserve the time limit or other charac terlstics of the relaywheneverIthe-overloafl' 70" J" is so great that unless some suitable pro- 5 vision is made the timelimit of the relay;

for example,v will be seriously-changed prefer to obtain the desired result by som'e; means which acts somewhat like a'kindof 76 verting from the current carrying lpa l ts of the dev ce the excess current resultmgffrom a the extreme cond tlon, such as a severe over- 2 1 l c load on the e'lectriccircuit, and in. way; 80" 51:: v I shield or protect the device fromithe'excess current which would otherwise interfere with the operation or change the --characteristics or the device. For example, Imay use a reactance or similar device so rel'sdzedto 85 The variousfeaturesof inventionwill be 1 6; more particularly described in the accoln panying specification and pointed outglnthe ,1,

appended claims. 1 My My invention will best be understoodfin; connection with the accompanyin drawi in which merely for purposes ofi ustration' I have shown some of the various forms in which my invention may be embodied, and L, in which Figure-l is a diagramfof'a re1ay;,.

embodying one form of my inventi i Fig;

2 is a diagram of a relay embodying another form; Fig. 3 isa diagram show ng-a'dlfier r ent modification; Fig; 4 1s. a d agram show;

cut type of relay.'

ing still another form of embodiment of my. invention; Fig. 5 1s adlagram showing one' way of applying my invention to 'polyphase. systems; and Fig. 6 is a diagram showing an embodiment of my invention in a differ- In the'particular .form of electro-responsivedevice shown in Fig. 1, which for convenience is shown as a time limit relay, the circuit breaker or other means for controlling the circuit' to be protected is controlled through some suitable form of control or tripping-circuit, not shown, and containing the cont-acts 1 which cooperate with the bridging contact 2 to closev the tripping circuit and thereby cause the circuit breaker to open the circuit to be protected. The movement of the contact 2 is retarded by any suitable form 'of retarding device such as a bellows {retarding de yice 3; The" contact 2 is moved into operative engagement with the contacts 1 by any suitable movable'niember of there-.

lay, such as the core l which moves the contact 2 against the resistance of the retarding" device 3. An actuating coil or-winding 5 moves the member or core lupward when energized. This actuating winding" is supplied with current through-an energizing circuit 6 which is in any conveneient way,

as for example by a current transformer,

supplied with currentderived from the circuit-to be protected. When an abnormal condition, such as an overload, for example,

occurs upon the circuit which is to be pro-- tected, the actuating winding 5 is energized and the member or core 4 is moved upward at a rate which'is controlled by the retarding device or bellows 3. As the current'in theenergizing circuit Sisroughly proporQ tiolia'l to the amount of overload on the main circuit a very severe overload or short circuit would cause the actuating winding 5 "to exert. avery strong pull upon the core 4 and overpower the retarding device 3 unless some suitable provision is made to guard against its action.

b ass for the excess current, and thus auto-' matically shield the winding 5from the excess. current. In the particular arangement shown in Fig. 1, I provide electroreactive means such as the coiL7 conected in shunt to the actuating winding 5 J andmounted in inductive relation to. a magnetic circuit or iron or other suitable material proportioned to saturate Whenever thelciir' rent" in the circuit to be protected reaches a value. great enough to derange the pro-,-

tective device. As long as the magnetic cir; cuit of the reactive wind ng 7 is below saturation the winding exerts its full reactive effect and comparatively "little currentwill flow through it, but as soonasthe/inagnetic oes not- "increase with the current, and for excess circuit saturates the reactive efiect I l current the electrorea'ctive means acts substantially as a resistance and permits most of the excessive current to flow through it, so that .the

excess current isshunted or diverted from theactuating winding 5 as long as the magnetic" circuit of the reactive winding 7 is saturated. Although the re.- actance in shunt to the actuating winding 5 may be constructed in any suitable way a compact. and simple device can be made as shown'in Fig. 1 by' utilizing anironframe "8 having across bar 9 and a core 10 for the magnetic circuit of the reactive winding 7 .and alsofor part of another magnetic c 11 cuit which includes the core 4: and is ener gi zed by the actuating winding 5. By s uitably proportioning or' adjusting the parts 8, 9 and 10, there 1s secured for the reactive winding 7 a magnetic circuit which will saturate upon any desired amount of overload upon the circuit to be protected.

The operation of this device is as follows:

ll/hen an overload appears upon the circuit to be protected current flows through the en ergizi'ng circuit 6 and the actuating winding 5, whereupon the winding 5 exerts upon the member or core 4 a. force approximatelv proportional to the amount of overload. As long as the overload on the main circuit is below a predetermined limit the magnetic circuit of the reactive winding 7 is not saturated, and the reactiveefi'ects prevents any,

great amount of current from flowing through the winding 7. As the overload increases the amount of current in the energizing circuitfi also increases until at a predev termined limit the magnetic circuit of the re active winding 7 becomes saturated, whereupon it begins to modify or control the action of the winding 5 in such a way that even though the overload increases far beyond the predetermined limit, nevertheless the 'force exerted by the winding 5 upon the member or core 4; increases only a comparatively slight amount. The result is that up to apredetermined limit the force exerted upon the movable member or core a is approximately directly proportionalto the amount of overload, but as soon as the overload exceeds a predetermined limit an increase in overload very slight increase in the force exerted upon the member 4. As a result the retardlot .125 beyond that limit causes a comparatively ing device 3 is able to control the movement 7 of the member 4 under all conditions and all overloads, and'the time limit of the protective device-is practically unaltered even on very heavy overloads.

- In the modification shown in Fig. 2, the 5 reactance is exterior to the protective de vice and, comprises a winding 11 mounted upon a magnetic circuit 12 which is proportioned to saturate at a certain definite amount of current on the'main circuit. The reactance l1 modifies or controls the action ot the winding 5 ingtlte same Way as thedevlce shave-n in Figllw In Fig. 3 I have showna modification in which the action of the actuating winding of -the relay is' modified or controlled,. at lea'st"in part, throughthe energizing circuit 6. y In this particular form of my invention the energizing fcircuitfi receives its current througha transfor' "1 ,13 comprising .-a.,secongl ar winding I v cted directly 7 p n'r'g zingcircuit G and a primary I winding;=. pplied from the current trans- "ZIOI IDEIFTQ" j which supplies current derived from the circuit to be protected. The iron the transformer 13 is so proportioned enthe current in the circuit to be 1 unt the iron core is saturated. When thisloccurs the current in the main circuit can increase to a verygreat amount, yet there would be onlya comparatively slight increase-in the amount of currentin the energizing circuit 6, since the ratio of the transformer 13 changes as soon as its core 35. becomes saturated, and as long as the core is saturated excessive currents may flow through the primary withoutproducing corresponding amounts of currentin the energizing circuit 6.

In'Fig. 4T have shown a modification of vmy invention in which the energizing cir-' Qjcuit 6 supplies current to an actuating wind- -.ing 15 and also a control winding 16 connected in series with the actuating winding and provided with a magnetic circuit which saturates when the current in the main cireu'it reaches a predetermined limit. The co1ls 15 and"1'6are wound to oppose each other and are so related that when'the magnetic-circuit of the control coil 16 becomes saturated the control coil will exert a modifying or controlling effect which counteractsto a large extent the effect of the actuating coil 15. In the particular form shown the relay is made with the iron frame 8, as shown in Fig. 1, and the control c011 16 is wound upon the core 10. As in the form of device shown in Fig. .1, the magnetic circu t through the upper part of the frame 8 and the parts 9 and 10 is so proportioned that it saturates when the current in the maln clrcuit reaches a' definite limit.

The operation of this form ofthe device is as follows: As long as the magnetic errcuit of the control coillfi Is not satur t forc e exerted uponthemember or core a 'lIlCIBZlSGS only a comparatively slight-"ex'-.

cted reaches a certain predetermined a manner which is common in watt-meters and is well understood. In accordance with the lines of force generated by that coil re. main in the iron and do' not-afi'ect the field set up by the actuating winding 15.' When the magnetic circuit of the "winding 16 be--* comes saturated, any further increase in current will cause; a stray-magnetic. fieldwhich counteracts or opposes the'ma'gnetic field set up by the winding 15 and consequently modifies or controls the effect of the Winding 15 upon the member 4 to such 75,. an extentfithat even though the current .in', the main circuit increases very materially above the limit at which the magnetic circuit of the coil 16 became saturated, yetithe tent. Asv a result-of; this co-action of the windings the retarding device 3 is able to, control the core under practically all conditions of overload. Q35 To facilitate understanding ofmy in.- I vention, I have shown and described in the preceding figures relays which are adaptedfor single-phase circuits, but my invention is equally applicable to polyphase circuits. Merely for purposes of illustration I have shown diagrammatically in Fig. 5 oneway of applying relays similar, to the relay shown in Fig. 1 to a. three phase circuit. Each phase of the circuit is provided with a relay having a current'coil 5 energized 4 by current dependent upon the current in the phase to which it is' connected. 'Any one of the relays can control the three phase circuit through a common tripping circuit,

17. In the particular arrangement shown the tripping circuit is normally open, and is supplied from some suitable local source such as storage battery 18. Whenever the tripping circuit is closed by any oneof the three relays, the trip coil 19 is energized and opens the three phase circuit by means of some suitable form of'switch not shown.

My invention is also applicable" to'many other forms ofdevices than relays, andmay be applied equallywell to any form of relay which responds to conditions upon an electric circuit. In Fig. 6 I have shown diagrammatically a disk type of relay embodying one form of my invention. In this particular figure the tripping contacts. 20 are driven through suitable connections- 21 from the disk 22, which is actuated by potential coils; 23'and a current coil 24 in my invention I modi'fy the effect of excessive currents-upon the relay by means of an automatic bypass or shunt'for controlling the-current coil 24, thisshunt bein formed of 'reactance 25 connected inpara lel with the current coil Q L'and proportioned t0 pro-J tect the current coil 24 from the effects of excessive currents in the circuit 26.

a My invention may-be embodied in' many other forms than those illustrated and dcscribed, and therefore I do not limit my invention to the precise arrangement disclosed except in so far as it'is limited by the scope ofthe a pended claims.

What .claimjas new and desirejto secure by Letters-Patent of the United States, is

1. A protective device comprising a movable 1118 531110 member, retarding means for opposing movement of said member, two WlllClIIlgS, said member being movable in ,re-

sponse to abnormal current'in one of said- .Windings, and an iron inductive relation to sald W'1nd1n s proportloned to saturate when the current in one of-sald windings exceeds a predetermined limit.

' 2. A protective device for electric circuits comprising a retarded movable circuit controlling member, a yoke of magnetic materialshaped to provide one magnetic circuit including said movable member and another distinct magnetic circuit, an actuatingwinding' for energizing the first magnetic' circuit to move said member, and a second Winding in inductive relation to the other magnetic circuit and proportioned to saturate said other magnetic circuit upon the occurrence of apredetermined overload upon the-circuit to be protected,

3. A protective device for electriedcircuits comprising an actuating winding 7 I Witnesses:'

responsiveto abnormal conditions in the clrcuit to be protected, a retarded circuit controlling member actuated by said Wind-- ing, a second Winding mounted coaxially With said actuatingwinding and Wound to 1 control the effect of said actuating windin upon said circuit, controlling member, an

a magnetic circuit in inductive relation to] said. second Winding proportioned to saturate upon the. occurrence. of. .an overlo'ad which exceeds a predetermined value.

at. A protective device-comprising a'mov-- able circuit controlling member, an iron yoke providing 'two' magnetic circuits,- an

. actuating Winding operatively related to one normal conditions above a predetermined amount I In Witness whereof, I have hereunto set vmy hand this'5th day of August,' 1913.

EDWARD M. HEWLETT.

BENJAMIN E. Hunt, -Hnnnn @mronn. 

